PRESURE IN FULE TANK

1995 Geo Prizm

1995 Geo Prizm 4 cyl Two Wheel Drive Manual 200K miles

I have replaced my fule tank twice with new tanks and they keep getting small cracks in them. I am being told I have to much presure in the tank since I have also replaced my gas cap. I have noticed that from time to time my engine is making a different sound then normal. Can you tell me what mit be causing the extra presure in the tank that would effect my engine and how I can fix it?